Satellite Fixed Services (FSS), including Very Small Aperture (VSAT) satellite systems, will continue to coexist with terrestrial wireless communication links, such as microwave tower-to-tower links, and 5th Generation (5G) wireless systems. In a star topology, which is common in modern high throughput satellite networks, the gateway site can be protected from interference by appropriate site planning and/or shielding. The remote terminals, though, may be located substantially anywhere and have different cost constraints than gateway sites and therefore can be more susceptible to terrestrial interference.
Directional antennas are one technique that can reduce some types of terrestrial interference to VSAT end user terminals. However, factors including proximity of terrestrial interference sources compared to the propagation distance to the satellite, the current cost-performance for directional VSAT end user antennas, ranges of transmitted power for fielded microwave links, and power limits for satellite beam transmission, can render the directional antenna technique inadequate for a range of applications.
An additional technical matter that bears on the difficulty of an economical solution to this terrestrial interference is that current high throughput satellites typically use a single carrier, with time division multiple access (TDMA), and coding such as Digital Video Broadcast (DVB)-S2x. In an adaptive white Gaussian noise (AWGN) environment, this TDMA implemented DVB-S2x is generally acceptable. However, interference at user terminals from terrestrial microwave towers can be narrowband in comparison to the DVB-S2x bandwidth, which can significantly degrade the current single carrier TDMA approach.
One technique for reducing total signal loss from narrowband interference is to apply a more robust coding. This technique, though, can have technical shortcomings. One is that a more robust coding generally lowers the TDMA signal's effective data rate, not only for the TDMA time slot assigned to the end user terminal receiving the interference, but for all of the TDMA time slots, and therefore for all end users serviced by the TDMA beam. In addition, in certain applications, received interference power level can have such magnitude that robust coding can cease to be a practical solution.
For reasons as identified above, there exists a need for an economical and effective solution to terrestrial narrowband interference at remote end user terminals, particularly in satellite based communication systems.